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<title>Data Set Element</title>
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<h1>DataSet</h1>

<p>Parent of simple data set and joint data set.</p>

<h3>Description</h3>
<p></p>
<h3>See Also</h3>
	
<h2 class="property">computedColumns</h2>

<p>User-defined columns in the result set.</p>

<h3>Description</h3>

<p>A computed column is a user-defined column produced as an 
expression of other columns within the data set�s primary result set. It is not 
of the columns retrieved directly from the underlying data provider.</p>

<h3>See Also</h3>

<h2 class="property">parameters</h2>
<p>Defines the data access attributes of the list of input and/or output parameters.</p>
<h3>Description</h3>
<p>Many data sets allow parameters, which can be of input and/or output modes. For some, the user must define the parameters as part of the data set definition. For other data sets, the driver itself can provide the set of parameter definitions from the information available in a data set query. In the latter case, parameter definitions are derived data and <i>are not</i> stored in the parameter definition.</p>
<p>Some drivers refer to a parameter by position. Others can refer to a parameter by name. Also, for some data sets, the data set definition can omit parameter definitions for optional parameters not used within the report. &nbsp;Not all parameter properties are required. If a property is omitted. BIRT assumes that the data set implementation can provide it at run time. If the driver cannot provide the information, then a runtime error occurs.&nbsp;This is an optional list of data set parameter definitions, used only when the underlying data provider cannot provide this information.&nbsp;When contradicting meta-data are found between those provided dynamically by a data provider and&nbsp;those specified in a data set definition, the data provider&iuml;&iquest;&frac12;s meta-data takes precedence.</p>
<h3>See Also</h3>
<p><code>ComputedColumn</span> structure</p>

<h2 class="property">columnHints</h2>

<p>Defines the report-related data attributes of the result set�s columns.</p>

<h3>Description</h3>

<p>In BIRT, a result set column can be defined with an 
alias.&nbsp; Aliases are useful in cases where a column name is awkward, or is used 
by multiple columns in a result set.</p>

<p>BIRT reports provide a rich viewing experience. The user 
can search the report, extract data to a file, export data to an OLAP system, 
and more. Such operations work on the actual data set�s result set instead of on 
the presentation of the data. Column hints let the report developer customize 
the search and data extract experience.</p>

<p>The column hint element provides a number of &quot;hints&quot; 
about result set columns. The hints override BIRT defaults for how columns are 
handled during viewing. Hints can be provided for both retrieved and computed 
columns.</p>

<p>Column hints are keyed to the data set�s primary result 
set using names. The user must understand how to keep the hints in sync with the 
data set when either the data set definition, or underlying data source, 
changes.</p>

<p>BIRT uses the column hints in the following cases:</p>

<ul>
<li>The report references a column using the alias defined in the column hint.</li>
<li>The report references a column (retrieved or computed) that is also referenced by the column hint.</li>
<li>The column hint has the Export attribute set to &quot;always&quot;.</li>
</ul>

<p>In each case, BIRT checks whether the data set provides 
the requested column. If so, it continues processing the report.&nbsp; If not, it 
issues a fatal runtime error.</p>

<h3>See Also</h3>
<p><code>ColumnHint</span> structure</p>

<h2 class="property">filter</h2>

<p>An optional set of filters to apply to the result set before any other data transforms.&nbsp;</p>

<h3>Description</h3>

<p>An optional set of filters that apply to the data set�s 
primary result set.&nbsp; A data set�s filter is applied to each row of the retrieved 
result set before any other data transforms.&nbsp; The filter expression should thus 
not contain any aggregation functions.&nbsp; It usually references at least one 
column from a data row, and may also reference a report parameter or other 
scripting variable.</p>

<h3>See Also</h3>
<p><code>Filter Criteria</span> structure</p>
<p>Listing <code>filter</code> property</p>
<p>ListingGroup <code>filter</code> 
property</p>

<h2 class="property">cachedMetaData</h2>

<p>Cached derived data attributes of a data set.</p>

<h3>Description</h3>

<p>Defines the cached derived data attributes of a data 
set. The BIRT designer uses the cached 
information until the user initiates refresh and reconciles with the latest 
derived data attributes provided by the connected data source. This 
property is used during report design time only; its content is maintained by 
the BIRT designer tool.</p>

<h3>See Also</h3>
<p><code>CachedMetaData</span> structure</p>
	
<h2 class="property">sortHints</h2>

<p>List of sort hints which support row ordering.</p>

<h3>Description</h3>

<p>List of sort hints which support row ordering.Sort hint can be mapped to ODA corresponding values.</p>

<h3>See Also</h3>
<p><code>SortHint</span> structure</p>

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